Polyamides



Patented Oct. 3, 1939 UNITED STATES PATENT OFFICE POLYAMIDES No Drawing.

Application September 22, 1936,

Serial No. 102,053

13 Claims.

This invention relates to polymeric materials, and more particularly tonew polyamides.

In my applications Serial Numbers 180 and 181, filed January 2, 1935,now Patents Nos.

2,071,253 and 2,130,523, I have disclosed polyamides which are capableof being drawn into strong fibers showing upon X-ray examination typicalfiber orientation along the fiber axis. The polyamides most useful forthis p rp se are those in which the chain of atoms constituting therecurring structural unit contains either no unsaturated carbon tocarbon linkages, or contains unsaturation of the benzenoid type only.Thus, polyamides derived from amino acids of i5 formula NHzRCOOH andfrom diamines of formula NHzR'NH: plus dicarboxylic acids of formulaHOOCR."CO0H, in which R, R and R" are divalent hydrocarbon radicals freefrom nonbenzenoid unsaturation, are for the most part 20 high-meltingcrystalline solids which can be obtained in the form of superpolyamides,that is, products which can be spun into filaments that can becold-drawn into oriented fibers. These superpolyamides are generallyinsoluble in most 25'organic solvents with the exception of phenols andcertain acids.

I have now found that the polyamides containing unsaturated carbon tocarbon linkages of the non-benzenoid type, although less useful in the30 production of fibers, possess properties such as solubility inconventional organic solvents which make them useful for variouspurposes to which the fiber-forming polyamides claimed in the abovementioned applications are not adapted.

5 The present invention is concerned with these unsaturated polyamides.

This invention has as an object the preparation of new and usefulpolymeric products. A further object is the production of polyamides 40which are useful in the coating and in other arts.

Other objects will appear hereinafter.

The polyamide-forming reactants, as described in the above mentionedcases, are substances which on heating alone or in admixture with an- 45other reactant (complementary polyamide-forming reactant) are capable ofyielding a polyamide. These substances include polymerizablemonoaminomonocarboxylic acids, amide-forming derivatives ofpoiymerizable monoaminomonocar- 50 boxylic acids, diamines, dicarboxylicacids, and amide-forming derivatives of dibasic carboxylic ocids. In thepreparation of polyamides, a diamine requires as a complementarypolyamideforming reactant a dicarboxylic acid or amide- 55 formingderivative thereof, while a dicarboxylic acid or its derivativesrequires a diamine as a complementary polyamide-forming reactant. In thespecification and claims the term dibasic carboxylic acid" will be usedto include dicarboxylic acids and amide-forming derivatives of dibasic 5carboxylic acis. The term amide-forming derivatives will be used tocover esters, anhydrides, amides, and acid halides.

In the present invention the polyamide-iorming reactants, as forinstance a polymerizable l0 monoaminomonocarboxylic acid, contain anunsaturated linkage of the non-benzenoid type. Or if two reactants areused, as in the case of diamines and dibasic carboxylic acids, at leastone of the reactants must contain such unsaturation. The termnon-benzenoid unsaturation refers to aliphatic unsaturation, namely,oleflnic or acetylenic unsaturation, as distinguished from theunsaturation contained in the benzene ring of aromatic compounds.However. the unsaturation remaining in a benzene ring which has lost itsaromatic character by elimination (hydrogenation) of one or more of itspairs of double bonds is non-benzenoid unsaturation.

The polyamides of this invention may be derived from unsaturated aminoacids, the unsaturation preferably being present in the chain of atomsseparating the amino and carboxyl groups rather than in the branch orside chain. The most valuable polyamides of this invention, however, aremade by reacting a diamine with a dibasic carboxylic acid containingnon-benzenoid unsaturation, or by reacting a dibasic carboxylic acidwith a diamine containing such unsaturation, or by reacting a diamineand a dibasic carboxylic acid both of which contain nonbenzenoidunsaturation. It must be observed, however, that the amino groups of thediamine must be attached to aliphatic carbon atoms because iniusible andnon-resinous products generally result if diamines are used in which theamino groups are attached directly to aromatic carbon atoms. Moreover,only primary and secondary diamines, i. e., diamincs whose aminonitrogens each carry at least one hydrogen atom, can be used.

As a general method of carrying out my invention an unsaturatedpolymerizable monoaminomonocarboxylic acid (including amideformingderivatives thereof) or a mixture of substautially chemical equivalentamounts of a primary or secondary diamine and a dibasic carboxylic acid,at least one of which contains an unsaturated non-benzenoid linkage, areheated in the presence or absence of a solvent to reaction temperature,which is usually IOU-300 C., and preferably -275 0., until a polymer ofthe desired properties is formed. The reaction may also be carried outin the presence of a diluent which is a non-solvent for the polymer. Thereaction is a condensation polymerization involving the removal of theby-product water, alcohol, phenol, hydrogen chloride, or ammonia,depending upon the derivatives of the said acid used. The heating may becarried out in an open or closed reactor under ordinary, reduced, orincreased pressure. Usually it is desirable to carry out the reactionunder conditions which permit the removal of the water or otherbyproducts formed in the reaction. It is desirable to carry out thereaction in the absence of air, and it is sometimes advantageous to addan antioxidant. Generally it is unnecessary to add a catalyst; althoughinorganlc-substancesof alkaline reaction, such as oxides and carbonates,and acid substances such as halogen salts of polyvalent elements, e. g.,aluminum, zinc, and tin, are sometimes helpful.

When the polyamide is prepared from a di-- amine and a dibasiccarboxylic acid, the first reaction which occurs on bringing thereactants into suiiiciently intimate contact is the formation of adiamine-dicarboxylic acid salt. It is often desirable to separate andpurify this salt prior to its conversion into the polyamide. The saltsare generally crystalline, are readily purified by orystallization froma, suitable solvent, such as water or alcohol, and have definitecompositions. The preparation of the salts affords an automatic means ofadjusting the amine and acid reactants to substantial equivalency andavoids the difliculties attendant upon the preservation of the isolatedamine in the state of purity. The formation and purification of thesalts also tends to eliminate impurities present in the original diamineand dibasic acid.

The polyamides of this invention as initially prepared containunsaturated linkages of the non-benzenoid type, that is, an olefinic oracetylenic linkage. This unsaturated linkage appears in the divalenthydrocarbon radicals separating the recurring amido groups in thepolymer molecules. The position of the unsaturated linkage and the orderand frequency or its occurrence in the polymer molecule are dependentupon the reactants used in the preparation of the polymer. If thepolymer is obtained exclusively from a polymerizablemonoaminomonocarboxyllc a c i d NHZRCOOH, in which R. is a divalenthydrocarbon radical containing an unsaturated linkage of thenon,-benzenoid type, then this unsaturated linkage will be present ineach recurring unit (-NHRCO) in the polyamide. If the polymer is derivedfrom a mixture of saturated and unsaturated polymerizable amino acids,the unsaturated linkage will oi. course appear less frequently in thepolymer molecule. It is evident that several types of unsaturatedpolyamides of the diamine-dibasic acid type can be prepared; forexample, those in which the diamine (NHzRN'Hz) represented isunsaturated, those in which the dibasic carboxylic acid (HOOCR"COOH) isunsaturated and those in which both the amine and acid are unsaturated.In the formulae R and R" represent divalent hydrocarbon radicals one orboth of which contains an unsaturated linkage of the non-benzenoid type.The unit length of the recurring units of the resulting polyamide is thesum of the radical lengths of the dlamine and the dibasic carboxylicacid used in its preparation. Thus, the unit length of the polyamidegiven in the first example below is 16 since it is made from fumaricacid and decamethylenediamine, whose radical lengths are 4 and 12,respectively. The recurring structural unit of this unsaturatedpolyamide may be represented as follows:

4 ization of amino acids where the reacting groups are the amino andcarboxyl groups oi? different molecules and the product has therecurring unit 0 11 eat.

or whether the polyamide results from the interaction of the aminogroups of a diamlne with the carboxyl groups of a dibasic carboxylicacid and the product has the recurring unit 0 o n n H II I I are allcharacterized by the fact that the structural unit of the polyamideconsists of a chain of atoms having an unsaturated (olefinic oracetylenic) divalent hydrocarbon radical situated between a nitrogenatom attached to aliphatic car bon and a carbonyl group. In other words,my polyamides comprise the reaction product of one or more reactantswhich provide interacting amide-forming carboxyl and amino groups, saidamino groups being attached to aliphatic carbon atoms and having atleast one hydrogen atom attached to each nitrogen atom, theamide-forming groups in at least one of said reactants being separatedby an intermediate hydrocarbon radical containing an unsaturatedcarbon-carbon nonbenzenoid linkage.

Still further combinations are possible by using saturated diamines anddibasic carboiwlic acids along with the unsaturated diamine and/orunsaturated dibasic carboxylic acid. It is also possible to usepolymerizable monoaminomonocarboxylic acids in conjunction with adiarnine and a dibasic carboxylic acid, at least one of said reactantsbeing unsaturated. It is evident therefore that at least one of thereactants used in the preparation 01' the products of this inventionmust have the formula XRY in which X and Y represent amino or carboxylgroups (or their equivalents) and R represents a divalent hydrocarbonradical containing an unsaturated nonbenzenold linkage. On hydrolysiswith strong mineral acids the products of this invention in generalyield the reactants from which they were derived, the amino constituentsbeing obtained in the form of their mineral acid salts.

The following examples, in which parts are given by weight, areillustrative of the prepara-- tion and application of the products ofthis inventlon:

EXAMPLE I Poluamide from fumaric acid and decamethylenediamine Elevenand six-tenths (11.6) parts 01' Iumaric acid was heated with 18 parts ofdecamethylenediamine and 30 parts of phenol for 30 minutes at ISO-160 C.and then for 20 minutes at ISO-160 C. under 1-2 mm. absolute pressure toremove the phenol. A light-colored, friable resin was obtained whichmelted at 45-50 C. This product could be transformed into an infusibleand insoluble resin by heat treatment, possibly as a result ofpolymerization through the unsaturated oleflnic linkages.

Exmm II Poll/amide from maleic acid and decamethylenediamine Eleven andsix-tenths (11.6) parts of maleic acid was heated with 18 parts ofdecamethylenediamine and 30 parts of phenol for 50 minutes at -160 C.;during the last 20 minutes of heating the pressure was reduced to 2 mm.and the phenol distilled. An amber-colored, elastic, heathardenableproduct was obtained which slowly hardened upon standing at roomtemperature.

ExAuPLnIDI Polyamide from acetylenedicarborylic acid anddecamethylenediamz'ne Eleven and tour-tenths (11.4) parts of acetylenedicarboxylic acid was dissolved in 50 parts of ethanol and added to asolution of 18 parts of decamethylenediamlne in 50 parts of ethanol. Thesolution was allowed to stand overnight to complete crystallization ofthe acetylenedicarboxylic acid-decamethylenediamine salt. The yield ofsalt was 24 parts. This salt was heated with an equal weight of phenolfor 1.5 hours at -16550. The pressure was then reduced to 5 mm. and theheating continued for a period of six hours, the temperature beinggradually raised to 230 C. The resulting resin, a polyamide containingan acetylenic linkage, was reddish brown in color and somewhat plasticat room temperature. It was soluble in ethanol and in the ethyl ether ofethylene glycol.

EXAMPLE IV Polyamide from mucom'c acid and ethylenediamine A mixture of7.1 parts of muconic acid HOOCCH=CHCH=CHCOOH, and 3.3 parts ofethylenediamine was dissolved in 50 parts of hot water. Sufficientethylenediamine was added to make the solution neutral to litmus. Thecrystalline diamine-dibasic acid salt which separated upon cooling wasdissolved in an equal weight of phenol and heated for 1.5 hours at200-210 C. The phenol was then removed by 20 minutes additional heatingunder reduced pressure. A reddish brown, hard resin was formed whichsoftened at about 61 C. It was soluble in certain ethanolbenzenemixtures, in'the ethyl ether of ethylene glycol, and in 10% aqueoussodium hydroxide.

EXAMPLE V Pol amide from mixed dihydronaphthalenedicarborylic acids anddecamethylenediamine Sixty and five-tenths (60.5) parts ofdecamethylenediamine was heated with 77 parts of a mixture of 1,2- and1,4-dihydronaphthalene-1.2- and 1,4-dicarboxylic acids for 2.25 hours at220- 225 C. A soft plastic resin was obtained which was soluble inethanol. Films of the resin upon Polyamide from decamethylenediamine and1,4-

dihydronaphthaZene-I,4-dicarborylic acid Eleven (11) parts ofdecamethylenediamine was heated for one hour at 200-225 C. with 14 partsof 1,4-dihydronaphthalene-1,4-dicarboxylic acid,

CH CH-COOH C OH 0 J\ /OH 0 CH-CO0H The resultant polyamide was a clear,ambercolored, hard, brittle resin. It softened at about 57 C. and wassoluble in ethanol, dioxan, and in the ethyl ether of ethylene glycol.

EXAMPLE VII Polyamide from heramethylenediamine and dihydromuconic acidA solution of 12.5 parts of hexamethylenediamine in 100 parts of ethanolwas added to a solution of 14.4 parts of dihydromuconic acid(HOOCCH2CH=CHCH2COOH) in 250 parts of hot ethanol. The diamine-dibasicacid salt which separated out melted .at 189-191" C. A solution of 23parts of the salt in 25 parts of mixed cresols was heated for five hoursby means of the vapors of boiling naphthalene. The cresol was thenremoved under reduced pressure at C. The residue (polyamide) thusobtained was an ambercolored, alcohol-soluble, resin which softened atabout 35 C.

It will be noted from the examples that the polyamides of this inventioncan be prepared in the presence or absence of a solvent. Especiallyuseful solvents in the preparation of the polyamides are monohydriophenols, such as phenol itself, the cresols, xylenols, hydroxydiphenyls,and the like. However, nonsolvents for the polymer, such as high-boilinghydrocarbons, may also be used. When easily volatile reactants are used,e. g., ethylenediamine, it is desirable to carry out at least theinitial stage of the reaction in a closed reactor or under reflux toprevent loss of reactants. The products of this invention areconveniently prepared in an open reactor equipped with a refluxcondenser which permits the water or other by-products of the reactionto escape but not the reactants or solvent. During the lat ter stage ofthe reaction it is often advantageous to decrease the pressure in orderto complete the reaction and, if desired, to distill off the solvent.However, the product can be removed from the solvent by precipitationmethods.

The polyamides of this invention are prepared by reacting the diamineand dibasic acid in sub stantially equal molecular proportions. This isnecessary in order to obtain highly polymeric, water-insoluble products.It is possible, however, to obtain water-insoluble polymeric productssuitable for use in coating and molding compositions by using as much as10% excess of either reactant.

The examples cite a number of polyamides derived from the reaction ofvarious unsaturated dicarboxylic acids with various diamines. Asexamples oi. other unsaturated acids that may be used in the preparationof the unsaturated polyamides of this invention might be mentionedmesaconic acid, itaconic acid, glutaconic acid, and glutinic acid. Whena readily polymerizable acid is used, the polyamide is oftencontaminated with some of the acid polymers (Example V). In certaincases some addition of the diamine to the unsaturated linkage in thedibasic acid also occurs. Additional examples of diamines which may bereacted with the unsaturated dibasic carboxylic acids aretetramethylenediamine, pentamethylenediamine, heptamethylenediamine,octamethylenediamine, nonamethylenediamine, and p-xylylenediamine.Unsaturated diamines may also be used.

The polyamides in the foregoing examples are derived from unsaturateddibasic carboxylic acids and saturated diamines. Unsaturated polyamidesare also obtained by reacting unsaturated diamines, e. g.,NH2-CH2--CH=CH-CHz-NH2,

and

with dicarboxylic acids or amide-forming derivatives of dibasiccarboxylic acids, such as dibutyl carbonate, diethyl oxalate, malonicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, and p-phenylenediacetic acid.

It is evident from the above discussion that many combinations ofreactants are possible in the preparation of the polyamides of thisinvention. Further combinations are possible by reacting one or morediamines with one or more dibasic carboxylic acids, at least one ofwhich contains an unsaturated non-benzenoid linkage. Similarly,interpolymers can be prepared from the reaction of one or moremonoaminomonocarboxylic acids with diamine-dibasic carboxylic acidmixtures, in which 'one reactant contains an unsaturated linkage.Moreover, it is within the scope of this invention to mix preformedpolyamides, at least one of which contains an unsaturated nonbenzenoidlinkage. The products of this invention can be mixed with otherpolymers, e. g., superpolyamides of the types described in theapplications previously referred to. Thus it is possible to addsubstantial amounts of an unsaturated polyamide to a superpolyamide, e.g., polyhexamethylene adipamide, and obtain a product whose propertiesclosely resemble those of the unmodified superpolyamide; the mixedpolymer can be spun from melt into filaments capable of being cold drawninto oriented fibers.

The polyamides of the present invention which are derived frompolyamide-iorming reactants containing an unsaturated carbon-carbonnonbenzenoid linkage are generally resinous condensation products. Theseproducts, at least when first prepared, are distinguished from thosedescribed in the above mentioned applications in that the polyamidesclaimed herein are soluble in quite a range of solventsand are thereforemore adapted to the preparation of coating, impregnating, sizing,adhesive and molding compositions than those prepared from polyamideswhich do not contain the unsaturated linkage. The products may also beused in the preparation of fibers, but for this purpose it is generallydesirable to incorporate them with a fiber-forming ingredient, such as acellulose derivative or a fiber-forming superpolymer of the typedescribed in the applications identified above.

The products of this invention, as indicated above, are for the mostpart resinous, varying in softening temperature and solubilitycharacteristics, depending upon the reactants from which they wereprepared. In general they are soluble in such solvents as alcohol,dioxan, and ethers of ethylene glycol. They are insoluble in water. Forthe most part they have good compatibility characteristics and can bemixed with drying oils, various resins, cellulose derivatives,plasticizers, and other ingredients which are used in the preparation ofcoating and plastic compositions. Many of the products are of theheat-hardening type, i. e., they can be converted by heating orsometimes by contact with air into insoluble products.

As many apparently widely diiierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. The polymeric reaction product of compounds consisting substantiallysolely of equimolecular proportions of bifunctional polyamide formingreactants the sum of whose radical lengths is at least 9, theamide-forming groups in said reactants being attached to aliphaticcarbon atoms, at least one of said reactants containing an unsaturatedcarbon-carbon linkage of the nonbenzenoid type in the chain separatingthe amideforming group,

2. A polyamide consisting substantially solely of the reaction productof one or more bifunctional reactants the sum of whose radical lengthsis at least 9 and which provide substantially equimolecular proportionsof interacting amideforming carboxyl and amino groups. said amino groupsbeing attached to aliphatic carbon atoms and having at least onehydrogen atom attached to each nitrogen atom, the amide-forming groupsin at least one of said reactants being separated by an intermediatehydrocarbon radical containing an unsaturated carbon-carbonnon-bcnzenoid linkage in the chain separating the amide-forming groups.

3. A polyamide obtainable by condensation polymerization from reactantsconsisting substantially solely of chemically equivalent amounts of adibasic carboxylic acid and a diamine in which the amino nitrogens areattached to aliphatic carbon atoms and each carry at least one hydrogenatom, said dibasic carboxylic acid having an unsaturated carbon-carbonnon-benzenoid linkage in the chain of atoms separating the carbonylgroups, said diamine and dibasic carboxylic acid being selected suchthat the sum of their radical lengths is at least 9.

4. A polyamide obtainable by condensation polymerization from reactantsconsisting substantially solely of chemically equivalent amounts of adibasic carboxylic acid and a diamine in which the amino nitrogens areattached to aliphatic carbon atoms and each carry at least one hydrogenatom, said diamine having an unsaturated carbon-carbon non-benzcnoidlinkage in the chain of atoms separating the amino groups, said diamineand dibasic carboxyllc acid being selected such that the sum of theirradical lengths is at least 9.

5. A polyamide having its nitrogen atoms attached to aliphatic carbonatoms and derived subarrears to stantially solely from amoncaminomonocarboxv ylic acid having a radical length of at least 9 andcontaining a hydrocarbon radical having an unsaturated carbon-carbcnnon-benzenoid linkage in the chain making up the recurring structuralunit of the polyamide.

6. A process which comprises heating under polyamide-forming conditionsreactants consisting substantially solely of chemically equivalentamounts of bifunctional polyamide-forming reactants the sum of whoseradical lengths is at least 9 and one of which contains an unsaturatedcarbon-carbon non-benzenoid linkage in the chain separating theamide-forming groups, the amide-forming groups in said reactants beingattached to aliphatic carbon atoms;

7. A process for making polyamides which comprises heating underpolyamide-forming conditions reactants consisting substantially solelyof chemically equivalent amounts of bifunctional polyamide-formingreactants the sum of whose radical lengths is at least 9, said reactantsbeing a dibasic carboxylic acid and a diamine in which the aminonitrogens are attached to aliphatic carbon atoms and each carry at leastone hydrogen atom, at least one of said reactants containing anunsaturated carbon-carbon non-benzenoid linkage in the chain of atomsseparating the amide-forming groups.

8. A process for making polyamides which comprises heating untilresinification takes place a monoaminomonocarboxylic acid as asubstantially sole reactant, said acid having its amideforming groupsattached to aliphatic carbon atoms and having a radical length of atleast 9 and containing a hydrocarbon radical having an unsaturatedcarbon-carbon non-benzenoid linkage in the chain separating theamide-forming groups.

9. A polyamide consisting substantially solely of recurring structuralunits oi chain length of at least 9, said units having the generalformula in which R and R. are divalent hydrocarbon radicals at least oneof which contains an unsaturated carbon-carbon non-benzenoid linkage inthe chain making up the recurring structural units.

10. A poiyamide consisting substantially solely of recurring structuralunits having a radical length of at least 9 and having the generalformula in which R is a divalent hydrocarbon radical containing anunsaturated carbon-carbon linkage of the non-benzenoid type in the chainmaking up the recurring structural units.

11. A polyamide consisting substantially solely of the reaction productof chemically equivalent amounts of bifunctional polyamide-formingreactants and having its nitrogen atoms attached to aliphatic carbonatoms and having a radical length of at least 9, said polyamide yieldingon hydrolysis with strong mineral acids a polyamide-forming reactant offormula XRY in which X and Y represent amide-forming groups and Rrepresents a. divalent hydrocarbon radical con taining an unsaturatednon-benzenoid linkage in the chain making up the recurring unit of thepolyamide.

12. The polyamide set forth in claim 3 in which said dibasic acid ismaleic acid.

1 13; The polyamide set forth in claim 3 in which said 'dibasic acid isdihydronaphthalene dicarboxylic acid.

WALLACE HUMCE CARO'I'HERS.

